A conventional method of roll transfer coating adhesive with some sort of pattern onto a moving strip-shaped item being coated is that of Japanese Application 9-90798, owned by the assignee of the present invention. This conventional method, as shown in FIG. 2, discloses an adhesive coating method comprising a step in which adhesive is packed by doctor blade 54 into depressions in first roll 53, which has a surface upon which a first pattern of depressions is formed and which is immersed in hot melt adhesive 52 stored in adhesive tank 51; a step in which second roll 55, which has a surface upon which a second pattern or projections is formed, is brought into contact with the aforesaid first roll 53, and first roll 53 and second roll 55 are caused to rotate and adhesive is transferred from the first roll's depressions to the second roll's aforesaid projections; and a step in which the item being coated 56 is compressed at the aforesaid second roll 55 while being moved and the adhesive is transferred from the projections of the second roll 55 to the surface of the aforesaid item being coated 56. In addition, FIG. 2 shows a pressure roll 57, a nip roll 58, and a material 59 being glued on. This coating method is superior in that a fine dense pattern can be coated by combining the depression pattern of first roll 53 with the raised pattern of second roll 55.
However, the previously described coating method has the following problems. Namely, the amount of adhesive coated on the item being coated is determined by the depth of the depressions formed on the surface of the first roll, so it is difficult to regulate increases or decreases in the amount of adhesive coated, and if one wishes to change the amount of adhesive coated it is necessary to replace the roll with one in which the depth of the depressions has been changed.
Also, the hot melt adhesive in the adhesive tank in which the first roll is immersed is retained while being heated for long periods, so it is likely to degrade, and depending on the type of adhesive, changes in viscosity may occur, making stable coating impossible.
Ideally, all of the adhesive loaded into the depressions in the first roll would be transferred to the second roll, but there is not always a 100% transfer. In such cases the small amount of adhesive remaining in the first roll depressions carbonizes due to continuous operation over long periods and reduces the depth of the depressions, and in the worst-case scenario completely plugs the depressions. In such cases the first roll must be removed from the apparatus and cleaned, necessitating much time for disassembling and rebuilding the apparatus.
Also, the first roll is equipped with a doctor blade, but adjusting this requires considerable expertise, and if the doctor blade does not contact the roll with equal insertion pressure along the entire width of the roll, there will be irregularities in the adhesive coating and quality will suffer. Also, since the doctor blade is constantly in contact with the first roll, and if insertion pressure weakens due to wear, adhesive will not be confined to depressions but will also adhere to the roll surface outside depressions, so this adhesive too will be transferred to the item being coated, causing contamination and decreases in quality, and resulting in destruction of the fine dense coating pattern.